1. Field of the Invention
This invention relates to visual inspection systems, more particularly to inspection systems for micromechanical devices.
2. Background of the Invention
Visual inspection systems can be used to inspect electronic integrated circuits and devices. The inspection systems help the manufacturer verify that all of the parts are present and undamaged, or if they are operable, depending upon the device being inspected.
These types of inspection systems typically include a vision system, a controller, such as a personal computer, and a stage for loading the device under the vision system for inspection. Some devices have unique requirements that are not met by current visual inspection systems. One example of these are micromechanical devices.
These devices are unique because of their size and their operating characteristics. Some integrated circuits that do not require visual inspection can be tested by probe cards and voltage characterizations. Some devices must be inspected visually. Micromechanical devices need both.
Because these devices typically have moving parts, the vision system checks for defects in the moving parts. Additionally, since these devices are usually activated by voltage, their voltage characteristics must be tested.
One type of micromechanical device that exemplifies these needs is a micromechanical spatial light modulator. These modulators typically have an active surface that moves in response to a signal, thereby modulating incident light into an image. Examples of these include digital micromirror device (DMD.TM.) or the actuated mirror array (AMA.TM.). Both of these are reflective spatial light modulators. Transmissive spatial light modulators are less complicated to inspect, since one just lays them on the inspection stage and shines light through them to verify operation. With reflective spatial light modulators, the light must comes in at an angle and reflects up the appropriate optical axis to the vision system. Additionally, the moving parts of these devices must have proper electrical connection. However, all types of micromechanical devices would benefit from this type of inspection.
Therefore, some type of visual inspection system is required that can perform both visual inspection and operational testing.